"Apple on Monday said that it plans to release the promised update to iOS 4.2 for iPad, iPhone, and iPod touch. The update brings a number of long-awaited iOS 4 features to the iPad and adds the new AirPlay and AirPrint features for all iOS devices. In somewhat of a surprise, owners of the latest iOS devices can now use the Find My iPhone feature for free."

I can't understand why they made the find my iPhone service free only for the latest generation devices (iPhone 4, iPod touch 4G and iPad). I am of course a little bitter, since I own a 3GS, but I really can't see a reason.

The reason probably is to encourage hardware upgrades, but this is usually not Apple's MO. Their MO frequently is "We will screw the old generation if there is a technical reason", but not "We will screw the old generation just to force them to upgrade".

I can't understand why they made the find my iPhone service free only for the latest generation devices (iPhone 4, iPod touch 4G and iPad). I am of course a little bitter, since I own a 3GS, but I really can't see a reason.

The reason probably is to encourage hardware upgrades, but this is usually not Apple's MO. Their MO frequently is "We will screw the old generation if there is a technical reason", but not "We will screw the old generation just to force them to upgrade".

I'm guessing they did this because many older generation phones might be 2nd hand (ie Apple didn't make money from that individual on the sale of the iPhone)

Replying to myself here, but now that I did try it myself, I just got a "Device not supported" message. I read that you can associated your Apple id with Find My iPhone on a iPhone 4/iPad/iTouch 4 and then use it on an older device, but is there something specific you can do to activate directly on a 3GS?